Functions and structure of the urinary system
The human urinary system includes organs responsible for the formation, accumulation and excretion of urine from the body.
The system is designed to cleanse the body of toxins, hazardous substances while maintaining the desired water-salt balance.
Let's consider it in more detail.
The structure of the human urinary system
The structure of the urinary system includes:
The basis is the kidneys
The main organ of the urinary tract. Consist of kidney tissue designed to purify the blood with the release of urine, as well as to collect and excrete urine.
The kidneys perform many functions:
- Excretory. It consists in the removal of metabolic products, excess fluid, salts. Leading importance for the proper functioning of the body is the conclusion,. When their concentration in the blood is exceeded, intoxication of the body occurs.
- Water balance control.
- Blood pressure control. The body produces renin, an enzyme characterized by vasoconstrictor properties. It also produces a number of enzymes that have vasodilating properties, such as prostaglandins.
- Hematopoiesis. The body produces the hormone erythropoietin, due to which the regulation of the level of erythrocytes, the blood cells responsible for saturating tissues with oxygen, is carried out.
- Regulation of the level of proteins in the blood.
- Regulation of water and salt metabolism, as well as acid-base balance. The kidneys remove excess acids and alkalis, regulate the osmotic pressure of the blood.
- Participation in the metabolic processes of Ca, phosphorus, vitamin D.
The kidneys are abundantly supplied with blood vessels, which transport a huge volume of blood to the organ - about 1700 liters per day. All blood in the human body (about 5 liters) is filtered by the body about 350 times a day.
The functioning of the organ is arranged in such a way that the same volume of blood passes through both kidneys. However, with one of them, the body will adapt to new conditions. It is necessary to pay attention to the fact that with an increased load on one kidney, the risks of developing related diseases also increase. 
The kidneys are not the only excretory organ. The same task is performed by the lungs, skin, intestines, salivary glands. But even in the aggregate, all these organs cannot cope with the cleansing of the body to the same extent as the kidneys.
Normally functioning kidneys maintain homeostasis - the constancy of the internal environment, regulating the volume of fluid removed from it.
For example, at a normal level of glucose, its entire volume is absorbed back. With an increase in its concentration, part of the sugar remains in the tubules and is excreted along with urine.
ureteral canal
This organ is a muscular canal, the length of which is 25-30 cm. It is an intermediate section between and the bladder. The width of the canal lumen varies along its length and can range from 0.3 to 1.2 cm. 
The ureters are designed to move urine from the kidneys to the bladder. The movement of fluid is provided by contractions of the walls of the organ. The ureters and urinary tract are separated by a valve, which opens to remove urine, then returns to its original position.
Bladder
The function of the bladder is to accumulate urine. In the absence of urine, the organ resembles a small bag with folds, which increases in size as the fluid accumulates.
It is riddled with nerve endings.
The accumulation of urine in it in a volume of 0.25-0.3 liters leads to the supply of a nerve impulse to the brain, which manifests itself as an urge to urinate. In the process of emptying the bladder, the two sphincters are simultaneously relaxed, the muscle fibers of the perineum and the press are involved. 
The amount of fluid released per day varies and depends on many factors: ambient temperature, the amount of water drunk, food, sweating.
The ureters and bladder are made up of 3 layers. The first layer is the mucous membrane. It lines the organs from the inside, protecting the epithelium from the effects of salts. The next layer is muscle fibers, which, by contracting, promote fluid.
They are equipped with receptors that respond to signals from the kidneys to move urine or close a valve. The latter is the wall of the organ that attaches it to the fiber.
Structure of the urethra
It is a tubular organ that carries urine to the outside. Men and women have their own characteristics in the functioning of this part of the urinary system.
Whole system functions
The main task of the urinary system is the elimination of toxic substances. Blood filtration begins in the glomeruli of nephrons. The result of filtration is the selection of large protein molecules that are returned to the bloodstream.
The protein-free fluid enters the tubules.
The kidneys carefully and accurately select all the substances useful and necessary for the body and return them to the blood.
In the same way, they filter out poisonous elements that need to be brought out. This is the most important work, without which the body would die. 
Most of the processes in the human body proceed automatically, without human control. However, urination is a mind-controlled process and, in the absence of disease, does not occur spontaneously.
However, this control does not apply to innate abilities. It is produced with age during the first years of life. At the same time, girls form faster.
At the stronger sex
The functioning of organs in the male body has its own nuances. The difference concerns the work of the urethra, which ejects not only urine, but also sperm. The male urethra is connected to ducts from
bladder and testicles. However, urine and semen do not mix.
The structure of the urethra in men includes 2 sections: anterior and posterior. The main function of the anterior section is to prevent the penetration of infections into the distant section and its subsequent spread.
The width of the urethra in men is about 8 mm, and the length is 20-40 cm. In men, the canal is divided into several parts: spongy, membranous and prostatic.
In the female population
Differences in the excretory system are present only in the functioning of the urethra.
In the female body, it performs one function - the excretion of urine. The urethra is a short and wide tube, diameter
which is 10-15 mm, and the length is 30-40 mm. Due to anatomical features, women are more likely to experience bladder diseases, since infections are easier to get inside.
The urethra is localized in women under the symphysis and has a curved shape.
In representatives of both sexes, the occurrence of pain, retention or incontinence of urine indicates the development of diseases of the urinary organs or those located next to them.
In childhood
The process of kidney maturation is not completed by the time of birth. The filtering surface of an organ in a child is only 30% of that in adults. The nephron tubules are narrower and shorter.
In children of the first years of life, the organ has a lobular structure, there is an underdevelopment of the cortical layer.
To cleanse the body of toxins, children need more water than adults. It should be noted the benefits of breastfeeding from this point of view.
The breast milk entering the child's body is completely absorbed, so the need for excretion of waste products is small. However, when replacing mother's milk with other foods, an increase in the load on the organ is observed.
There are differences in the work of other organs. The ureters in children are wider and more tortuous. The urethra in young girls (under the age of 1 year) is completely open, but this does not lead to the development of inflammatory processes.
Conclusion
The urinary system contains many organs. Violations in their work can lead to serious disorders in the body. With the accumulation of harmful substances, signs of intoxication appear - poisoning, which spreads to the entire body.
At the same time, diseases of the urinary system can be of a different nature: infectious, inflammatory, toxic, caused by circulatory disorders. Timely contacting a doctor in the event of symptoms indicating a disease will help to avoid serious consequences.
